Newbie configure error

I'm trying to configure for a PHP make with the following options: shell> ./configure --with-zlib-dir=/usr/local --with-libjpeg=/sw --with-libtiff=/sw --with-libpng=/sw --with-gd --with-pgsql=/usr/local --with-mysql=/usr/local/mysql --with-xml --with-dom=/sw --with-apxs When I hit return, it seems to run fine for a minute or two as it gathers system info but then it halts with the following error <snip> checking whether to enable truetype string function in GD... yes checking for fabsf... yes checking for floorf... yes If configure fails try --with-jpeg-dir=<DIR> configure: error: libpng.(a|so) not found. I rummaged around and found a symbolic link to the libpng.a file which points to libpng12.a both of which are located at the same level in my /sw/lib directory so I'm not sure what the problem is. And as for the line "If configure fails try --with-jpeg-dir=<DIR>" I really don't understand what it wants. A directory containing source for a jpeg library? A directory containing a jpeg library? What? I'm still pretty new to unix (only about 2 weeks) so I'm a little puzzled by all this, any help would be greatly appreciated. Thanks, Ken